Here is Larry Sabato's contribution to the literature: A More Perfect Constitution: 23 Proposals to Revitalize Our Constitution and Make America a Fairer Country:
He outlines his argument in this LA Times article. He suggests that war powers have tilted too far in favor of the executive, the Senate is too unrepresentative of the population to still be legitimate, the presidential selection process is biased in favor of unrepresentative states, and that its time to allow foreign born citizens the right to run for president. He also points out that the founders would probably be surprised that the document has survived more or less intact this long (though the reinterpretation has been significant).
A web site has launched which outlines his suggestion.
Sabato is a serious, thoughtful person, but I don't know how serious his suggestion is. Considering the controversies that surround relatively light weight issues like SCHIP (my apologies to those who depend on the program) I can't imagine how difficult it would be to manage a convention. There is always that chance that unforeseen, small mistakes could have huge consequences. But it's a useful exercise to consider what we would revise if we could.